February 29th is a leap day, so what scientific facts are hidden behind the leap day?

As we all know, leap year only appears once every four years, and February 29th only appears in leap year, so this day only appears once every four years.

If you happen to be born on this day, it means that you can have your birthday only once every four years. So why does leap day only appear once every four years? Why do you arrange the calendar like this?

The origin of leap day. The earth goes around the sun once a year for 365 days, 5: 48: 46. But the international calendar we use is only 365 days a year, which is nearly 6 hours more.

In this way, there will be nearly 24 extra hours on the calendar every four years, which is equivalent to one day. In order to narrow the gap as much as possible, leap day appeared.

If there is no leap day, our calendar will not keep up with the pace of natural development and change, which will cause confusion between seasons and dates.

Spring, summer, autumn and winter change all year round, and the four seasons change on the earth because there is an angle between the ecliptic plane formed by the revolution of the earth and the equatorial plane formed by the rotation of the earth, which is the intersection angle between the ecliptic plane and the equatorial plane, which is about 23 26'.

The existence of this included angle causes the earth to tilt during the revolution and rotation at the same time, so this tilt causes the earth to have four obvious seasons, because this tilt leads to the change of the direct solar point, just like the twenty-four solar terms often used in our lives, among which the four solar terms, the vernal equinox, the summer solstice, the autumn equinox and the winter solstice, are the most vividly distinguished, reflecting the regression movement of the direct solar point behind them.

At the vernal equinox of March 2 1, the direct point of the sun points to the equator, and then moves northward continuously. Summer solstice on June 22nd, pointing to the Tropic of Cancer, and then moving southward. On September 23, the autumnal equinox pointed to the equator again and then continued to move south. 12 Winter Solstice on June 22nd, pointing to the Tropic of Cancer.

The speed of the sun's revolution is also changing. The orbit of the sun is not a circle, but an ellipse, and the sun is the focus of the ellipse.

At perihelion in early July, the earth is farthest from the sun, and its revolution speed reaches the slowest.1perihelion in early October, the earth is closest to the sun, and its revolution speed reaches the fastest.

The origin of the calendar. The existence of calendars is of great help to our production and life. The ancient calendar in China was called the imperial calendar. Later, due to the progress of the times and the liberation of ideas, the imperial calendar was changed to the yellow calendar.

It is the crystallization of the labor and wisdom of the ancient people in China. Ten stems and twelve branches are arranged and combined in a fixed order and used repeatedly. Its content is also very extensive, which can reflect astronomical meteorology, climate season, and the best farming time and harvest season.

Therefore, people will not miss the best planting season and harvest season of each crop, and will not bring any trouble to people's lives, but will bring great convenience to people's production and life.

Now we have adopted the international calendar, that is, the solar calendar, which we also call the solar calendar, but we still have our own lunar calendar, that is, the lunar calendar, which has not been abolished. Our traditional festivals are still based on the lunar calendar. China's traditional culture can't be lost, which is a precious wealth handed down to us by the ancients and is worth inheriting and developing.

Conclusion. February 29th is a leap day that only occurs once every four years. After understanding it, we know that its existence is not superfluous, but has profound significance and rich value.

Its existence maintains the balance between the calendar we use, natural development and seasonal changes, so that our calendar can give us the best guidance in time to the greatest extent, and will not have too great an impact on our daily life and production activities as much as possible.